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From: Bozhidar Batsov <bozhidar.batsov@gmail.com>
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Subject: Re: if-let and when-let: parallel or sequential
Date: Mon, 11 Aug 2014 15:01:26 +0300
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On August 10, 2014 at 6:23:25 PM, Stefan Monnier (monnier=40iro.umontreal=
.ca) wrote:
> I noticed that the new =60if-let' and =60when-let' in trunk's subr-x cr=
eate =20
> their bindings sequentially (like =60let*' rather than =60let'). Would =
there =20
> be any interest in renaming these to =60if-let*' and =60when-let*', and=
 =20
> adding parallel-binding versions under the current names=3F =20

I have a hard time imagining a situation where the =22parallel=22 version=
 =20
would be useful. =20


Stefan =20


if-let and when-let don=E2=80=99t make much sense with more than one bind=
ing form. Other lisps (like Clojure) would raise
an exception if you try to bind more than a single form.

;; good
(if-let ((x (something)))
=C2=A0 =C2=A0 =E2=80=A6)

;; error
(if-let ((x (something))
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0(y (something-else)))
=C2=A0 =C2=A0 =E2=80=A6)

I=E2=80=99d suggest we do the same.=C2=A0
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<html><head><style>body=7Bfont-family:Helvetica,Arial;font-size:13px=7D</=
style></head><body style=3D=22word-wrap: break-word; -webkit-nbsp-mode: s=
pace; -webkit-line-break: after-white-space;=22><div id=3D=22bloop=5Fcust=
omfont=22 style=3D=22font-family:Helvetica,Arial;font-size:13px; color: r=
gba(0,0,0,1.0); margin: 0px; line-height: auto;=22>On August 10, 2014 at =
6:23:25 PM, Stefan Monnier (<a href=3D=22mailto:monnier=40iro.umontreal.c=
a=22>monnier=40iro.umontreal.ca</a>) wrote:</div> <blockquote type=3D=22c=
ite=22 class=3D=22clean=5Fbq=22><span><div><div></div><div>&gt; I noticed=
 that the new =60if-let' and =60when-let' in trunk's subr-x create
<br>&gt; their bindings sequentially (like =60let*' rather than =60let').=
 Would there
<br>&gt; be any interest in renaming these to =60if-let*' and =60when-let=
*', and
<br>&gt; adding parallel-binding versions under the current names=3F
<br>
<br>I have a hard time imagining a situation where the =22parallel=22 ver=
sion
<br>would be useful.
<br>
<br>
<br>        Stefan
<br>
<br></div></div></span></blockquote><br><div>if-let and when-let don=E2=80=
=99t make much sense with more than one binding form. Other lisps (like C=
lojure) would raise</div><div>an exception if you try to bind more than a=
 single form.</div><div><br></div><div>;; good</div><div>(if-let ((x (som=
ething)))</div><div>&nbsp; &nbsp; =E2=80=A6)</div><div><br></div><div>;; =
error</div><div>(if-let ((x (something))</div><div>&nbsp; &nbsp; &nbsp; &=
nbsp; &nbsp; &nbsp;(y (something-else)))</div><div>&nbsp; &nbsp; =E2=80=A6=
)</div><div><br></div><div>I=E2=80=99d suggest we do the same.&nbsp;</div=
></body></html>
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